Silicon carbide is a wide bandgap semiconductor that has great potential for many electronic applications. A key barrier to its widespread use is the inability to grow large diameter high quality substrates economically and of sufficient quality for electronic devices. There have been many attempts to grow silicon carbide on silicon to obviate these problems. However, the large lattice mismatch (25%) precludes the growth of good quality silicon carbide. The polytypism exhibited further complicates matters.
One method that is widely used to grow silicon carbide on silicon is to deposit a thin layer of carbon on silicon. The carbon is deposited either through heterogeneous gas phase nucleation or direct carbon deposition and then reacting this carbon to form a silicon carbon layer. The literature refers to this process as carbonization or carburization. This carbide layer acts as a seed for subsequent silicon carbide growth. The main problem with this method lies in the fact that the carbide template layer formed is highly defective.
Any defects in this initial layer will have a severe impact on the defect density of layers grown upon this carbonization layer as it is the seed for subsequent silicon carbide growth. The carbide template layer formed is highly defective, not only because of the lattice mismatch, but also due to the elevated temperatures that are required for the cracking of the various reacting gases (primarily hydrocarbons). The elevated temperatures increase the diffusion of silicon across the newly formed silicon carbide layers and lead to the formation of voids in this critical carbonization layer.
Moreover, at the present time, optical communications and silicon based logic are distinct technologies employing separate processing methods. A major problem in the development of direct bandgap semiconductors, for example, gallium nitride, as commercially viable materials for device applications is the lack of an adequate substrate.
Furthermore, currently, high temperature FET's based on silicon carbide are fabricated using very expensive silicon carbide one inch or two inch diameter substrates.